An Insect Virus 



the organism engenders while at work, waste 

 substances designated by the general appel- 

 lation of urinary products? 



To isolate these products, to collect them 

 separately, would scarcely be practicable, if 

 we did not have recourse to what follows on 

 the metamorphosis. Every Moth, on emer- 

 ging from her chrysalis, rejects a copious 

 mixture of uric acid and various humours of 

 which very little is as yet known. It may 

 be compared with the broken plaster of a 

 building rebuilt on a new plan and represents 

 the by-products of the mighty labours accom- 

 plished in the transfigured insect. These re- 

 mains are essentially urinary products, with 

 no admixture of digested foodstuffs. 



To what insect shall I apply for this re- 

 siduum? Chance does many things. I col- 

 lect, from the old elm-tree in the garden, 

 about a hundred curious caterpillars. They 

 have seven rows of prickles of an amber yel- 

 low, a sort of bush with four or five branches. 

 I shall learn from the Butterfly that they be- 

 long to the Great Tortoiseshell (Vanessa 

 polychloros, LlN.). 



Reared on elm-leaves under a wire-gauze 

 cover, my caterpillars undergo their trans- 

 177 



